The present invention relates to torque converters and pertains particularly to means for varying the capacity of the torque converter.
In the application of hydrodynamic torque converters to heavy-duty vehicle power trains it is often advantageous to be able to modify the basic power absorption and transmission capacity of the unit. This is especially desirable on machines having powered implements which are operated by power from the vehicle engine. In such machines it is often desirable to vary the proportion of power delivered to the implements and that delivered to the vehicle power train.
In many machines, such as front-end loaders, for example, the combined power demands on the engine from both the loaders', hydraulic pump and the power train can exceed the power available from the engine. This often results in excessive engine lugging and unsatisfactory performance of both the machine and the implement or loader bucket.
One approach to this problem has been the use of a slipping clutch. The clutch is disposed within the drive train to reduce the torque load imposed by the drive train. This approach is shown, for example, in U.S. Pat. No. 3,424,029 issued to J. Horsch et al on Jan. 28, 1969, and U.S. Pat. No. 3,478,621 issued to L. E. Johnson et al on Nov. 18, 1969, both of which are assigned to the assignee hereof. One problem with this approach is the short life that would normally exist in such a clutch under heavy working conditions -- that is, under conditions where the clutch is allowed to slip a considerable amount of time.
Another approach to this problem has been the use of variable pitch blades in the torque converter, particularly the stator blades of the torque converter. These systems, however, require complicated controls and mechanisms for the converter.